Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$240.81	13.179%	$272.5463	$272.55	$272.55	$272.50
Purchase #2	$80.89	12.472%	$90.9786	$90.98	$91.00	$91.00
Purchase #3	$140.63	9.619%	$154.1572	$154.16	$154.15	$154.20
Purchase #4	$166.70	9.647%	$182.7815	$182.78	$182.80	$182.80
Purchase #5	$9.60	5.194%	$10.0986	$10.10	$10.10	$10.10
Purchase #6	$211.64	12.622%	$238.3532	$238.35	$238.35	$238.40
Purchase #7	$177.81	10.716%	$196.8641	$196.86	$196.85	$196.90
7 purchase totals =	$1,028.08		$1,145.7795	$1,145.78	$1,145.80	$1,145.90